JPH1168705A - Two-way wdm optical transmission reception module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce crosstalk light of an LD light leaked to a PD light to be a non-problem level practically in the two-way WDM optical transmission reception module. SOLUTION: The two-way WDM optical transmission reception module is made up of an optical branch guide path formed on a plane substrate (Si substrate), a groove 10 provided to a branch part of the optical branch guide path, a dielectric multi-layer film filter 5 that is inserted in the groove 10 and branches an input light in a transmission direction and a reflection light depending on its wavelength, a transmission laser diode LD 3 and a reception photo diode PD 6 coupled optically with the optical branch guide path on the plane substrate 1. The transmission wavelength of the dielectric multi-layer film filter 5 is set to the reception wavelength of the reception PD 6 and a block wavelength of the dielectric multi-layer film filter 5 is set to the oscillation wavelength of the transmission LD 3 and the transmission LD 3 and the reception PD 6 are placed opposite to each other with the dielectric multi-layer film filter 5 inbetween.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength division multiplexing (hereinafter simply referred to as "WDM") optical transceiver module used in the field of optical communication or optical information processing.
In particular, in a WDM optical transceiver module in which a laser diode (hereinafter simply referred to as LD) and a photodiode (hereinafter simply referred to as PD) are hybrid-integrated on a quartz-based planar lightwave circuit, the wavelength multiplexer / demultiplexer is used. The present invention relates to a WDM optical transmitting / receiving module characterized in that the configuration is arranged to suppress crosstalk light.

[0002]

2. Description of the Related Art For example, a system in which an optical signal in the 1.3 μm band is used in the upstream and an optical signal in the 1.55 μm band in the downstream is studied, and a bidirectional WD for realizing this is studied.
M optical transmission / reception module
using silica-on-silicon optical motherboards ”Caro
le Jones et al., Integrated Photonics Research, Tec
hnical Digest IThB1, pp. 604-607, Boston, 1996.

FIG. 11 shows a schematic configuration of a WDM optical transmission / reception module described in the above document. In FIG. 11, 1
00 is an optical fiber, 101 is a substrate, 102 is an optical waveguide,
103 is a transmitting LD, 104 is a monitor PD, 105 is a directional coupler, 106 is a receiving PD, 107 is a receiving amplifier, 108 is a leak light blocking material, and 109 is a mirror.

[0004]

Generally, in a bidirectional system in which the wavelengths of upstream and downstream optical signals are changed, it is necessary to transmit and receive bidirectional communications simultaneously. Therefore, bidirectional WDM
One of the major problems of the optical transceiver module is to reduce crosstalk light that leaks oscillation light into its own receiving unit.

In the above document, the crosstalk light is reduced by arranging the receiving PD 106 so as to be orthogonal to the transmitting LD 103 (see FIG. 11). However, in this configuration, it is necessary to arrange the transmitting LD 103 and the receiving PD 106 orthogonally and to bend the waveguide from the receiving PD 106 to the directional coupler by 90 degrees. The size of the module also increases.

The light emitted from the transmitting LD 103 is:
The reflection point in the optical fiber transmission line returns to the module, and a part of it returns to the receiving PD1 via the directional coupler.
06. The amount of light returning to the receiving PD 106 is determined by the blocking performance of the directional coupler 105, but generally has a problem that sufficient blocking characteristics cannot be obtained.

An object of the present invention is to provide a technique capable of reducing crosstalk light, in which LD light leaks into PD light, to a practically acceptable level in a bidirectional WDM optical transceiver module.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0009]

In order to achieve the above object, the present invention provides an optical branching waveguide formed on a flat substrate, a groove provided at a branch portion of the optical branching waveguide, and A dielectric multilayer filter that is inserted into the groove and branches input light in the transmission direction and the reflection direction according to the wavelength; a transmission LD and a reception PD optically coupled to the optical branching waveguide on the flat substrate; A transmission wavelength of the dielectric multilayer filter is set to a reception wavelength of the reception PD, and a stop wavelength of the dielectric multilayer filter is set to a transmission wavelength of the transmission LD. The oscillation wavelength is set, and the transmitting LD and the receiving PD are arranged at positions facing each other with the dielectric multilayer filter interposed therebetween.

In the optical waveguide connecting the transmitting laser diode, the dielectric multilayer filter, and the receiving photodiode, a component of the light emitted from the transmitting photodiode that passes through the dielectric multilayer filter is included. A second dielectric multilayer filter to cut off is inserted.

That is, as a method for greatly reducing the crosstalk light of the conventional bidirectional WDM optical transmitting and receiving module, the present invention employs a wavelength multiplexer / demultiplexer using a dielectric multilayer filter, The most important feature is that the LD is arranged on the input / output fiber side (reflection port side) of the dielectric multilayer filter and the receiving PD is arranged on the opposite side (transmission port side).

Further, in the bidirectional WDM optical transmitting and receiving module, in the optical waveguide connecting the transmitting laser diode, the dielectric multilayer filter, and the receiving photodiode, the dielectric waveguide of the light emitted from the transmitting photodiode is provided. A second dielectric multilayer filter for intercepting a component transmitting through the body multilayer filter is inserted.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments (examples) of the present invention will be described below in detail with reference to the drawings.

In all the drawings for describing the embodiments (examples), those having the same functions are denoted by the same reference numerals, and their repeated description will be omitted.

(Embodiment 1) FIG. 1 is a diagram showing a schematic configuration of a bidirectional WDM optical transmitting and receiving module according to Embodiment 1 of the present invention, wherein 1 is a Si substrate, 2 is an optical waveguide, 3 is a transmission LD,
Is a monitor PD, 5 is a dielectric multilayer filter (wavelength multiplexer / demultiplexer), 6 is a receiving PD, 7 is an electric wiring, 8 is a Si terrace, 9 is a reinforcing glass, and 10 is a branch portion of an optical branching waveguide. The provided groove 11 is an optical fiber.

FIG. 2 is an enlarged sectional view taken along line AA 'of FIG. 1, FIG. 3 is an enlarged sectional view taken along line BB' of FIG. 1, and FIG. Are enlarged sectional views taken along the line CC ′ of FIG. 2 to 4, reference numeral 21 denotes a lower cladding layer (first lower cladding layer);
2 is a cladding layer for height adjustment (second lower cladding layer), 2
3 is a core of the optical waveguide 2, 24 is an upper clad layer, 25 is an adhesive for fixing the dielectric multilayer filter 5, 7A
Are electrical wiring and solder.

In the bidirectional WDM optical transceiver module of the first embodiment, as shown in FIGS. 1 to 4, a groove 10 is provided in a branch portion of an optical branch waveguide formed on a Si substrate 1. Into the groove 10 is inserted a dielectric multilayer filter 5 for splitting the input light in the transmission direction and the reflection direction according to the wavelength. A bidirectional WDM optical transmitting and receiving module comprising a transmitting LD 3 and a receiving PD 6 optically coupled to the optical branching waveguide on the Si substrate 1, wherein the transmission wavelength of the dielectric multilayer filter 5 is , The stop wavelength of the dielectric multilayer filter 5 is set to the oscillation wavelength of the transmission LD 3, and the transmission L
D3 and the receiving PD 6 are the dielectric multilayer filter 5
Are disposed opposite to each other.

The oscillation wavelength of the transmitting LD 3 is 1.3 μm.
m, the wavelength of light entering the optical fiber 11 is 1.55 μm
m, the wavelength of the emitted light is 1.3 μm. The transmission wavelength of the dielectric multilayer filter 5 is 1.55 μm, and the reflection wavelength is 1.
3 μm.

As described above, in the present invention, the wavelength multiplexer / demultiplexer using the dielectric multilayer filter 5 is employed, and the transmitting LD 3 is connected to the input / output fiber side (with respect to the dielectric multilayer filter 5). By disposing the receiving PD 6 on the opposite side (transmission port side) on the reflection port side,
Crosstalk light of the conventional bidirectional WDM optical transceiver module can be significantly reduced.

Next, a method of manufacturing a PLC platform will be briefly described with reference to FIG. First, a flat Si
By patterning the substrate 1, the transmitting LD3 / receiving PD6
Is etched to a depth of about 30 μm other than the Si terrace 8 on which is mounted. A glass layer serving as the lower cladding layer 21 is formed thereon by a flame deposition method (FIG. 5A). Thereafter, flattening polishing is performed until the Si terrace of the mounting portion of the transmitting LD3 / receiving PD6 is exposed on the surface (FIG. 5B). This surface serves as a height reference surface for the optical waveguide when the transmission LD3 / reception PD6 is mounted.

Subsequently, a height adjusting cladding layer (second lower cladding layer) 22 to be a height adjusting layer is provided. Next, a layer of the core 23 is deposited to about 7 μm (FIG. 5c). After etching the core layer into an optical waveguide pattern, an upper cladding layer 24 is deposited (FIG. 5d). Here, the flame deposition method was used for depositing the cladding layer and the core layer. Subsequently, only the transmission LD3 / reception PD6 mounting portion is etched until the Si terrace of the transmission LD3 / reception PD6 mounting portion is exposed again. Finally, the electrode wiring of the transmitting LD3 / receiving PD6 and the mounting solder 7A are deposited (FIG. 5e).

The transmission LD3 / reception PD6 is mounted and fixed to the mounting portion by solder reflow. For the method, see T. Hashimoto et al., “Hybrid integ
ration of spot-size converted laser diode on plana
r lightwave circuit platform by passive alignment
technique, ”IEEE Photon.Techno1.Lett., 8, No.11, pp.1
504-1506, 1996. Generally, LD
And the optical waveguide have different mode fields. Recently, research on a laser in which the mode field of an LD is expanded to improve coupling with an optical waveguide has been advanced. Nevertheless, at present, the coupling ratio between the LD and the optical waveguide is about 50%. For this reason, half of the light output from the LD is emitted into the cladding layer.

The method of forming the light branching section by the dielectric multilayer filter 5 shown in FIG. 1 is described in detail in the document Y. Inoue.
et al., ”Filter-embedded wavelength-division mult
iplexer for hybrid-integrated transceiver based on
silica-based PLC, "Electron.Lett., Vol.32, no.9, pp,
847-848, 1996.

The groove 10 for inserting the dielectric multilayer film of the dielectric multilayer filter 5 was formed with a width of 20 μm and a depth of 150 μm using a dicing saw. As the dielectric multilayer filter 5, for example, a filter having a thickness of 14 μm using a polyimide substrate was used. FIG. 6 shows the wavelength characteristics of the filter reflection type wavelength multiplexer / demultiplexer of the dielectric multilayer filter 5. As shown in FIG. 6, the dielectric multilayer filter 5 exhibits high isolation of up to 50 dB at the transmission port.

As shown in FIG. 1, since this excellent dielectric multilayer filter 5 exists between the transmitting LD 3 and the receiving PD 6, the 1.3 μm light emitted from the transmitting LD 3 into the cladding layer. Will not be coupled to the receiving PD 6. Specifically, the crosstalk light from which the output of the transmitting LD 3 leaks into the receiving PD 6 is about -70 dB. For this reason, 1.5, which is relatively lower in level than the 1.3 μm transmission signal,
5 μm light could be detected with high sensitivity by the receiving PD 6.

The bidirectional WD of this embodiment shown in FIG.
In the M optical transmitting and receiving module, even when 1.3 μm light transmitted to the optical fiber transmission line is reflected in the transmission line and returns to the module, the excellent stop band characteristic of the dielectric multilayer filter 5 allows the receiving PD 6 to be used. Can be sufficiently suppressed. For example, when the return loss at the reflection point in the transmission path is 30 dB, the crosstalk light coupled to the receiving PD 6 is -80 dB or less.

The bidirectional WDM optical transmitting / receiving module of FIG. 1 can separate the transmitting LD 3 and the receiving PD 6 from each other as compared with the conventional WDM optical transmitting / receiving module of FIG. For this reason, there is also a feature that the drive current of the transmitting LD 3 does not electrically leak into the photocurrent of the receiving PD 6.

For the sake of comparison, it is assumed that the circuit configuration of FIG. 1 is replaced as shown in FIG. In this case, the transmission L
Light emitted from D3 into the cladding layer passes through the dielectric multilayer filter 5 and is coupled to the PD 6 for reception. This 1.3
Since the level of the μm light is higher than the 1.55 μm light to be received, the receiving PD 6 cannot receive 1.55 μm with high accuracy.

In FIG. 1, 1.3 μm light is transmitted and 1.55 μm is transmitted.
The circuit configuration of the bidirectional WDM optical transmitting / receiving module for receiving the m light is shown.
A bidirectional WDM optical transceiver module for receiving m light can be realized by reversing the transmission wavelength and the blocking wavelength of the dielectric multilayer filter 5 as shown in FIG.

(Embodiment 2) FIG. 9 is a diagram showing a schematic configuration of a bidirectional WDM optical transceiver module according to Embodiment 2 of the present invention.

In the bidirectional WDM optical transmitting and receiving module of the second embodiment, a major problem is that the oscillation light of the transmitting LD 3 leaks into the receiving PD 6. In the first embodiment shown in FIG. 1, a circuit configuration is employed in which the first dielectric multilayer filter 5 that reflects the transmission LD 3 (1.3 μm light) is inserted between the transmission LD 3 and the reception PD 6. LD3 for transmission
(1.3 μm light) is prevented from leaking into the receiving PD 6. However, depending on the light source of the transmitting LD 3, 1.
Even when the light is oscillated at 3 μm, the spectrum may have a tail extending only to the 1.55 μm band.

In this case, in the circuit configuration shown in FIG. 1, of the light output from the transmitting LD 3, light in the 1.45 μm to 1.55 μm band that passes through the first dielectric multilayer filter 5 is received. Cannot be prevented from being bonded to the PD 6 for use. Therefore, as shown in FIG. 9, the transmitting LD 3 and the above-mentioned first dielectric multilayer filter 5 (1.3 μm reflection, 1.
Second to remove 1.55 μm light between
Of the dielectric multilayer filter 12 (1.55 μm reflection, 1.
(3 μm transmission) is inserted at an angle of 2 to 10 ° with respect to the waveguide. Here, the reason that the second dielectric multilayer filter 12 is tilted with respect to the waveguide is that the light reflected by the second dielectric multilayer filter 12 is recombined with the transmission LD 3 and the operation is unstable. It is to prevent that.

With the configuration shown in FIG. 9, only 1.45 μm to 1.5 μm output from the transmitting LD 3
It has become possible to prevent light in the 5 μm band from being coupled to the PD 6 for reception. Specifically, the efficiency of coupling of the oscillation light of the transmission LD 3 to the reception PD 6 before the insertion of the second dielectric multilayer filter 12 was −40 dB. The value could be reduced to -75 dB by inserting the dielectric multilayer filter 12 between the transmitting LD 3 and the first dielectric multilayer filter 5.

In the second embodiment, the case where the oscillation light wavelength of the transmission LD 3 (light source) is 1.3 μm and the reception light wavelength of the reception PD 6 is 1.55 μm is explained. 1.55 μm, the receiving light wavelength of the receiving PD 6 is 1.
In the case of 3 μm, a similar effect can be obtained by adopting the circuit configuration shown in FIG. That is, 1.3μ
Second dielectric multilayer filter 12A for removing m light
(1.3 μm reflection, 1.55 μm transmission) is inserted at an angle of 2 ° to 10 ° with respect to the waveguide, and the first dielectric multilayer filter 5A (1.55 μm reflection, 1.3 μm transmission) is inserted.

With the circuit configuration shown in FIGS. 9 and 10, crosstalk can be further reduced.

As described above, the invention made by the inventor has been specifically described based on the above embodiment (example). However, the present invention is not limited to the above embodiment (example), and the gist of the invention is as follows. Of course, various changes can be made without departing from the scope.

[0037]

As described above, according to the present invention, in the bidirectional WDM optical transmitting / receiving module, the crosstalk light leaking from the LD to the receiving PD is −70d.
Since it is extremely low as B, crosstalk light that leaks LD light into PD light can be reduced to a level that causes no practical problem. This makes it possible to obtain a bidirectional WDM optical transmitting / receiving module having high reception sensitivity.

Further, in an optical waveguide connecting the transmitting LD, the first dielectric multilayer filter, and the receiving PD, outgoing light of the transmitting LD passes through the first dielectric multilayer filter. By inserting a second dielectric multilayer filter that blocks components that cause crosstalk, crosstalk can be further reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of a bidirectional WDM optical transceiver module according to a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view taken along line AA ′ of FIG.

FIG. 3 is an enlarged cross-sectional view taken along line BB ′ of FIG. 1;

FIG. 4 is an enlarged cross-sectional view of a cross section taken along line CC ′ of FIG. 1;

FIG. 5 is a diagram for explaining a method of manufacturing a PLC platform.

FIG. 6 is a diagram illustrating wavelength characteristics of a filter reflection type wavelength multiplexer / demultiplexer of the dielectric multilayer filter according to the first embodiment.

FIG. 7 is a diagram for comparing the operation of the bidirectional WDM optical transmission / reception module (FIG. 1) of the first embodiment with the operation when the arrangement of each device is replaced.

FIG. 8 is a diagram for explaining the operation of the bidirectional WDM optical transceiver module according to the first embodiment;

FIG. 9 is a diagram illustrating a schematic configuration of a bidirectional WDM optical transceiver module according to a second embodiment of the present invention.

FIG. 10 is a diagram illustrating a schematic configuration of another bidirectional WDM optical transceiver module according to the second embodiment of the present invention.

FIG. 11 is a diagram showing a schematic configuration of a conventional WDM optical transmission / reception module.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Si board | substrate, 2 ... Optical waveguide, 3 ... Transmission LD, 4 ... Monitor PD, 5 ... First dielectric multilayer filter, 6 ... Reception PD, 7 ... Electrical wiring, 7A ... Electrical wiring and solder,
8 ... Si terrace, 9 ... reinforced glass, 10 ... groove, 11 ... optical fiber, 12 ... second dielectric multilayer filter, 21 ...
Lower cladding layer, 22 ... height adjusting cladding layer, 23 ...
Core of optical waveguide, 24: upper clad layer, 25: adhesive.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04B 10/14 10/04 10/06 (72) Inventor Yasufumi Yamada 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Inside (72) Inventor Yoshinori Hibino 3-19-2 Nishi Shinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (2)

[Claims] An optical branching waveguide formed on a planar substrate, a groove provided at a branch portion of the optical branching waveguide, and a transmission direction of input light inserted into the groove according to a wavelength and corresponding to a wavelength. A bidirectional WDM optical transmitting and receiving module including a dielectric multilayer filter that branches in a reflection direction, and a transmitting laser diode and a receiving photodiode that are optically coupled to the optical branching waveguide on the planar substrate, The transmission wavelength of the dielectric multilayer filter is set to the reception wavelength of the reception photodiode, the stop wavelength of the dielectric multilayer filter is set to the oscillation wavelength of the transmission laser diode, and the transmission laser diode and A two-way WDM, wherein a receiving photodiode is arranged at a position facing the dielectric multilayer filter.
Optical transceiver module. 2. The bidirectional WDM optical transmitting and receiving module according to claim 1, wherein the transmitting photodiode is provided in an optical waveguide connecting the transmitting laser diode, the dielectric multilayer filter, and the receiving photodiode. A bidirectional WDM optical transmission / reception module, wherein a second dielectric multilayer filter for blocking a component of the emitted light that passes through the dielectric multilayer filter is inserted.